The scholars differed as to when the time for doing ghusl on Friday begins. The majority (including the Shaafais, Hanbalis and Zaahiris) were of the view that it begins from dawn on Friday. This was narrated from Ibn Umar (رضي الله عنهما).
Al-Khateeb al-Sharbeeni (رحمه الله) said concerning the time for doing ghusl on Friday:
The time for that is the true dawn, because the reports connected it to the day, such as the words of the Prophet (blessings and peace of Allaah be upon him): Whoever does ghusl on Friday then sets out in the first hour So it is not valid if done before then.
And it was said: that the time for it begins halfway through the night as is the case on Eid.
Doing it close to the time when one goes for Jumuah prayer is better, because it is more likely to achieve the purpose of eliminating bad smells. If there is a conflict between doing ghusl and going early to the prayer, then paying attention to ghusl takes priority, as al-Zarkashi رحمه الله said: because there is a difference of opinion as to whether it is obligatory. End quote. [Mughni al-Muhtaaj, 1/558]
Al-Bahooti al-Hanbali (رحمه الله) said:
The beginning of its time is the break of dawn; doing ghusl before then is not valid but it is better to do ghusl just before going to Jumuah, because that is closer to achieving the purpose. End quote. [Kashshaaf al-Qinaa, 1/150]
Ibn Hazm (رحمه الله) said:
The first of the times for the ghusl mentioned is just after dawn breaks on Friday. we have narrated from Naafi رضي الله عنه from Ibn Umar رضي الله عنهما that he used to do ghusl after dawn broke on Friday, and that is acceptable as the ghusl for Jumuah. It was narrated from Mujaahid رحمه الله, al-Hasan رحمه الله and Ibraaheem al-Nakhai رحمه الله that they said: If a man does ghusl after dawn breaks, that is acceptable. End quote. [Al-Muhalla, 1/266]
According to Imam Maalik رحمه الله, the time for ghusl on Friday begins just before going to the prayer, and it is not acceptable except at the time of going; if a person does ghusl after dawn and does not go to the mosque straightaway, that is not acceptable and it is recommended for him to repeat it.
Al-Nawawi (رحمه الله) said:
if he does ghusl for Friday before dawn, that is not acceptable according to the sound opinion of our madhhab, and this is also the view of the majority of scholars, but al-Awzaai رحمه الله said that it is acceptable.
If he does ghusl for Jumuah after dawn has broken, it is acceptable in our view and in the view of the majority. This was narrated by Ibn al-Mundhir رحمه الله from al-Hasan رحمه الله, Mujaahid رحمه الله, al-Nakhai رحمه الله, al-Thawri رحمه الله, Ahmad رحمه الله, Ishaaq رحمه الله and Abu Thawr رحمه الله.
Maalik رحمه الله said: It is not valid except when going to Jumuah.
All of them say that it is not acceptable before dawn, apart from al-Awzaai رحمه الله who said: it is acceptable for him to do ghusl before dawn for both janaabah and Jumuah. End quote. [Al-Majmoo, 4/408; see also Haashiyat al-Adawi, 1/379; al-Taaj wal-Ikleel, 2/543]
The first view (that the time for it begins at the break of dawn) was favoured by Shaykh Ibn Baaz (رحمه الله). Shaykh Ibn Uthaymeen (رحمه الله) said: Ghusl for Jumuah begins at the break of dawn, but it is better not to do ghusl until after the sun has risen, because the day has certainly begun after sunrise, and because the time before sunrise is the time for Fajr prayer, and the time for Fajr prayer has not ended yet, so it is better not to do ghusl until after the sun has risen. Then it is better not to do ghusl until the time for going to Jumuah, so that he will be going to Jumuah immediately after purifying himself. End quote. [Majmoo Fataawa Ibn Uthaymeen, 16/142]